One-dimensional barcodes are widely used as optically readable means to store information. Within the past decade, two-dimensional barcodes have emerged to facilitate denser storage of data (see, for example, U.S. Pat. No. 5,128,525 to Stems et al., U.S. Pat. No. 5,940,135 to Petrovic et al., and U.S. Pat. Nos. 5,862,270 and 6,115,508 to Lopresti et al.). Commonly used formats for two-dimensional data encoding include, “Aztec Code,” “Data Matrix,” “Data Strip Code,” “MaxiCode,” “PDF 417,” “Micro-PDF 417,”and “QR Code.” Each of these conventional formats localizes data in characters or “glyphs” that are designed to facilitate machine reading.
Tamper evident seals and tags have been used for centuries, perhaps millennia, to secure and protect valuable information and articles. Currently, modern versions of these seals are used to secure some of the most dangerous articles created by mankind. The development of the “modern” tags and seals largely stopped in the 1970's, when the technology was deemed “mature” and unbreakable. Thirty years of technological innovations in printing, reproduction, computers, and robotics later, experts raise serious concerns about the security of these tags. Research into ultra-secure tags and seals has continued at a low level in the intervening years. Several promising technologies, e.g., glitter and fiber-optic tags have been developed that appear to be supremely difficult to counterfeit with no detectable differences. The trouble with these technologies is that the tamper evaluation requires sophisticated and time-consuming arrangement of evaluation apparatus, rendering the tags and seals inapplicable for use with walk-through inspections.
There is, therefore, a need in the art for tamper-indicating barcodes that provide a reliable and efficient way to determine if a barcode has been subjected to subtle or sophisticated tampering. Given the advances in copier and printing technologies, manipulation, alteration, and counterfeiting have become ever-present threats to the security of barcode-formatted data. The present invention relates to a novel tamper-indicating barcode that allows for detection of alteration to the barcode.